A semiconductor device obtained by flip-chip mounting a semiconductor chip on a circuit substrate is known as a mode of the semiconductor device. In this type of semiconductor device, the circuit substrate and the semiconductor chip are electrically and mechanically connected to each other through a connecting terminal referred to as a bump.
Also, an interval (gap) between the circuit substrate and the semiconductor chip is filled with a sealing resin referred to as an underfill material for protecting the bump being the connecting terminal. The underfill material fills the interval between the circuit substrate and the semiconductor chip by using a capillary phenomenon. At that time, a fillet flaring out at the bottom is formed on an outer periphery of the semiconductor chip, the fillet formed of the underfill material protruding out therefrom.
A thermoset resin such as an epoxy resin is used as the underfill material. Therefore, the underfill material in a liquid state is injected into the interval between the circuit substrate and the semiconductor chip to fill the same and thereafter cured by thermal treatment. At that time, warpage might occur on the circuit substrate by a stress associated with thermal contraction of a fillet-shaped protruding portion of the underfill material. Also, when a reliability test such as a temperature cycling test is carried out, the warpage might occur on the circuit substrate for a similar reason.
Therefore, technology of taking a measure by forming a sunken portion for preventing protrusion of the resin on a lower chip is suggested (refer to Patent Document 1).
Also, technology of reducing the warpage by using several types of sealing resins with different linear expansion coefficients is suggested (refer to Patent Document 2).
Furthermore, technology of reducing the warpage by providing a groove on a lower substrate is suggested (refer to Patent Document 3).